Having an aspi layer can be beneficial to programs. If you have Windows XP and are using DVD Decrypter to burn it will use XP's SPTI instead of aspi. Nero installs its own aspi but this will not work in conjunction with other programs only Nero, therefore, you would need an aspi layer. As to which aspi program to use I prefer Force Aspi, I found it easier to put in. Try this site for info